1. Field of the Invention
The invention relates to vacuum cleaner filtration. In one of its aspects, the invention relates to a vacuum cleaner having an improved filtration system. In another of its aspects, the invention relates to an improved post-motor exhaust filter for filtering particles downstream from a vacuum motor. In another of its aspects, the invention relates to an improved mounting for a post-motor exhaust filter. In another of its aspects, the invention relates to an improved pre-motor filter for filtering particles downstream from a dirty air separator.
2. Description of the Related Art
Upright vacuum cleaners have a main filtration or separation assembly for separating dust and debris from the working airstream that is drawn into the vacuum cleaner by the vacuum source. The main filtration assembly typically comprises a conventional filter bag or a centrifugal separator assembly. Vacuum cleaners that include cyclone separators are well-known in the art. Cyclone separator designs commonly employ frusto-conical shaped separators, while others use high-speed rotational motion of the air/dirt in a cylindrical separator to separate the dirt by centrifugal force. Typically, working air enters and exits at an upper portion of the cyclone separator while the bottom portion of the cyclone separator is used to collect debris. It is further known to employ multiple serial cyclone separators to improve the collection of fine debris particles that may not be collected by a single separator.
Vacuum cleaners further have at least one motor/fan assembly for generating suction to draw air and debris into the vacuum cleaner and, optionally, for driving an agitator, such as a brushroll, mounted in the foot of the vacuum cleaner. Alternatively, vacuum cleaners frequently have a vacuum motor/fan for generating suction airflow and a second dedicated motor assembly for driving an agitator. Air for cooling each motor/fan assembly is drawn into the vacuum cleaner and subsequently exhausted through separate ports in the vacuum cleaner housing. As the cooling air passes through the motor assemblies, carbon dust generated by the motor brushes can become entrained in the airstream and thus exhausted from the vacuum cleaner. The emitted carbon dust can lead to contamination of the home environment. To alleviate this contamination, the motor cooling air can be filtered after it has passed through the respective motors. On vacuum cleaners having both a vacuum and an agitator motor, separate filters can be placed at the respective exhaust ports to remove carbon dust from each motor cooling airstream, however, these filters can add expense and bulk to the vacuum cleaner. A high efficiency particle arrestor (HEPA) filter is commonly used for this purpose. To reduce expense and bulk and to improve ease of use, the vacuum and agitator motor cooling exhaust path(s) can be configured to pass through a single exhaust filter downstream from the vacuum and agitator motors to trap carbon dust together with any residual fine dust remaining in the air stream. The filter mounting location depends on unit architecture and is preferably configured to provide a hermetic sealing surface that is accessible by a user. A seal between the housing and the filter is important to prevent dust or other contaminates from escaping the vacuum cleaner into the home environment. It is desirable to implement a compact exhaust filter that is easily accessible and replaceable by a user and capable of containing residual dust and carbon particulates emitted by the system.
BISSELL Homecare, Inc. presently manufactures and sells in the United States an upright vacuum cleaner configured to port agitator motor cooling exhaust air to a working air conduit upstream of a vacuum fan inlet as disclosed in U.S. Patent Application Publication No. 20070209147, which is incorporated herein by reference in its entirety. The working air exits through a single HEPA exhaust filter that is mounted on a curved sealing surface at the side of the unit.